DE1922678A1 - Aluminium foil and thermoplastics film food - pack for salt foods - Google Patents

Abstract

Heat seal between base film and the biaxially stretched lid or cover film is torn to free the contents, and an anticorrosion layer is placed under this two-way stretched thermoplastics film component. Film used is pref. polypropylene used as a backing or cover for the basic aluminium foil.

Description

Easy-to-open packaging container has been used for several years Perishable food packaged in flat, sterilizable bowls.

The actual bowl consists e.g. of an aluminum band of Thickness 0.1 mm. The outside is covered with a colorless or colored layer of varnish approx. 0.05 mm thick, while the inside is covered with an unstretched polypropylene film 0.050 mm thick is laminated, the bowl is made of this composite film through produced a forming process similar to deep drawing. After filling the Schälohens With the contents to be packaged, a lid is made from a similarly constructed one The composite material is sealed onto the flat edge of the peel using pressure and heat. The finished packaging is then optionally sterilized.

Such bowls are opened for the purpose of removing the contents usually by cutting open along the sealing seam with the help of a pointed Knife. Because this type of order is unsatisfactory, there is another possibility of opening suggested. To do this, the aluminum band is attached to the lid instead of an unstretched one laminated with a thin biaxially stretched polypropylene film. Will the lid from this composite material to the SahWlchenrantl sealed, then the stretched polypropylene film shrinks in the vicinity of the sealing seam while at the same time Loss of strength. The lid is then expediently still with an over the edge of the lid protruding pull tab provided and it succeeds in this way the lid can be removed simply by tearing off without the aid of a tool, whereby the Polypropylene film tears along the sealing seam. The desired mechanical weakening of the polypropylene film near the sealing seam due to the shrinking process is from accompanied the formation of numerous pores in the propylene film and the one below The adhesive layer only provides imperfect protection for the aluminum tape. Will a chemically aggressive product is now packaged, such as strongly spiced, salty or acidic meat or fish products, then the aluminum corrodes under the pores the plastic film. This is why this convenient opening method has not yet been opened limited corrosive products.

According to the invention, this disadvantage is eliminated in that the aluminum strip of the lid on the inside under the adhesive layer and the heat sealable biaxially stretched plastic film has a corrosion protection layer. Against-.

The present invention is therefore an easy-to-open packaging container for aggressive filling goods made of laminated with thermoplastic plastic film Aluminum tape with a tearable heat-sealed seam between the foil of the The lower part and the biaxially stretched film of the lid is marked by a corrosion protection layer under the biaxially stretched thermoplastic Plastic film.

These biaxially stretched thermoplastic plastic films are made either high density polyethylene or polypropylene, the latter being preferred will. For the corrosion protection layer, for example, baked-in laokes are suitable on based on phenolic epoxy resins, 2-component reactive lacquers, in particular on Urethane base, for example Desmophen-Desmodur or from a purely physically drying one Paint? for example based on nitrocellulose, there is also the possibility of Instead of the paint as a corrosion protection layer, a plastic film with a high Softening temperature, e.g. from polyethylene terephthalate, between the aluminum and to apply the biaxially stretched heat-sealable plastic film.

In the drawing, FIG. 1 shows a packaging container according to FIG Invention, in which the lower part is a deep-drawn bowl and FIG. 2 the individual layers of the lid of such a container.

The bowl 1 consists of an aluminum strip 0.1 mm thick, which is provided on the outside with a layer of varnish 0.05 mm thick and Laminated on the inside with an unstretched polypropylene film 0.05 mm thick is. The edge of the peel is useful to increase the strength than Rolled edge 4 formed. The cover 2 is provided with a pull tab 3. being The structure from the outside to the inside is shown in FIG.

Herein are: A) A protective varnish that protects the aluminum against discoloration during sterilization by the water in the autoclave.

Nitrocellulose or stoving enamels are common for this, as are can be colored. The application strength is 2 - lo ggqm.

B) An aluminum strip made of soft or hard pure aluminum or alloys of aluminum, especially with manganese or magnesium. The thickness of the tape lies according to DIN 1784, sheet 2, in the range from 0.021 to 0.350 mm and is preferably 0.05 to 0.1 mm.

C) Corrosion protection layer according to the invention, application thickness 3 to 30 g / m², preferably 5 to 10 g / m².

D) The adhesive layer. Preferably 2 components are used here. Polyurethane adhesives used, the application rate is 3 to lo g / sqm.

E) A heat-sealable biaxially stretched plastic film, e.g. from Polypropylene or high density polyethylene from 0.01 to 0.025 mm, preferably 0.01 to 5 Up to 0.020 mm thick.

Apart from the fact that the plastic film of the lid is biaxially stretched is, according to the invention it always consists of the same material that is used for lamination of the container base is used. If a polypropylene film was chosen here, the heat-sealable inner layer of the lid also consists of a polypropylene film, which, however, is biaxially stretched to a slight open by tearing along to enable the sealing seam.

Have packaging containers constructed in the manner according to the invention has also proven its worth for chemically aggressive filling goods. For example wuSbn Deep-drawn bowls made from the above-mentioned composite material (lacquered aluminum strip o, ll mm, laminated with unstretched polypropylene (> o5o mm) with herrings in tomato sauce filled. The cans were sealed with a lid according to the invention Structure (from outside to inside) had: Melamine-epoxy paint: 4 g / sqm aluminum tape, soft: with 98.6 Al: 05 o70 mm phenol epoxy paint: 7 g / sqm 2-component polyurethane adhesive : 5 g / qm Biaxially oriented polypropylene film: 0.015 mm.

The sealing temperature was 220 ° C. with a sealing time of 0.5 seconds.

The bowls were then placed in the autoclave at a counter pressure sterilized from 2.8 atmospheres for 40 minutes at 1210C.

For comparison, some of the bowls were provided with lids that only by eliminating the phenol-epoxy paint used as a corrosion protection layer differ from the dedc eln according to the invention.

After six months of storage of the sterilized cans at normal The cans with the lids according to the invention showed no corrosion damage whatsoever at room temperature, while the lids without an anti-corrosion layer showed severe corrosion.

Claims (5)

P a t e n t a n s p r u c h e Easy-to-open packaging container for aggressive filling goods with a thermoplastic plastic film laminated aluminum tape with a tearable heat seal seam between the film. of the lower part and the biaxially stretched Foil of the lid is provided, characterized by a corrosion protection layer under the biaxially stretched thermoplastic plastic film. 2. Packaging container according to claim 1, characterized in that the plastic cover of the base and cover are made of polypropylene. 3. Packaging container according to claims 1 and 2, characterized in that; that the lower part is a deep-drawn bowl. 4. Packaging container according to claims 1 to s, characterized in that that the lid is provided with a pull tab. 5. Packaging container according to claims 1 to 4, characterized in that that the lower part has a rolled edge.